EP2788823B1

EP2788823B1 - Capillary flow control system for fluid indicator

Info

Publication number: EP2788823B1
Application number: EP12816501.6A
Authority: EP
Inventors: Lucien Vouillamoz
Original assignee: Preciflex SA
Current assignee: Preciflex SA
Priority date: 2011-12-06
Filing date: 2012-12-05
Publication date: 2016-11-16
Anticipated expiration: 2032-12-05
Also published as: JP2015505037A; CN104040439B; EP2788823A2; US20140326349A1; RU2014127561A; CN104040439A; WO2013084046A2; KR20140100563A; WO2013084046A3; CA2858300A1; WO2013084046A4; US10330233B2; JP6153536B2; RU2608062C2

Description

Background of the Invention

This invention relates to hydraulic fluid systems, and in particular, hydraulic systems used in consumer products in which at least two fluids occupy a single container, and the level of the interface between the fluids is to be adjusted.
Document US 4 229 975 illustrates a capillary bore to indicate temperature, said bore being provided with a constrictor to prevent the indicator liquid from returning into the reservoir bulb.
What is needed is a means of limiting fluid flow or restricting it to a controlled flow so that the fluids do not mix when a meniscus between the fluids is moved.

Summary of the Invention

A capillary system is provided for a fluid indicator according to claim 1. Other features of the invention as described in the dependant claims. The system includes at least one fluid restrictor, and a capillary channel or tube. The fluid restrictor has a small aperture formed therethrough. The capillary tube is adapted to receive at least two immiscible fluids. The fluid restrictor is sealingly affixed into at least one end of the capillary tube so that the small aperture communicates between the inside of the capillary tube and the outside of the capillary tube. The capillary tube is optionally treated so that an inner surface is oilophobic and hydrophobic. A fluid is pumped through the fluid restrictor into the capillary tube to move the meniscus formed between the fluids contained therein.
An object of the invention is better control of the interface or meniscus between the at least two fluids contained in the capillary tube, preventing mixing.

Brief Description of the Drawings

FIG. 1A is a top view of the fluid restrictor of the invention.
FIG. 1B is a cross-sectional side view of the fluid restrictor of the invention.
FIG. 1C is a perspective view of the fluid restrictor of the invention.
FIG. 2A is a top view of a first alternate embodiment of the invention.
FIG. 2B is a side view of the first alternate embodiment of the invention.
FIG. 3A is a top view of a second alternate embodiment of the invention.
FIG. 3B is a side view of the second alternate embodiment of the invention.
FIG. 4A is a top view of a third alternate embodiment of the invention.
FIG. 4B is a side view of the third alternate embodiment of the invention.
FIG. 5 is a cross sectional side view of a fourth alternate embodiment of the invention.
FIG. 6 is a perspective view of ends of the capillary tube of the invention, with fluid restrictors installed in the ends thereof.
FIG. 7 is a partial cross sectional view of the ends of the capillary tubes in which the fluid restrictors are installed.
FIG. 8 is a perspective view of a fluid restrictor installed half way into an end of a capillary tube.
FIG. 9 is a flow chart of the method of making the invention.
FIG. 10 is a perspective view of a fluid restrictor installed into an end of a capillary tube, in which there is an inadequate seal.
FIG. 11 is a perspective view of a fluid restrictor with an O-ring installed thereon, at an end of a capillary tube.
FIG. 12 is a flow chart of alternate method of making the invention.
FIG. 13 is a table of representative menisci created depending on the speed and viscosity of fluid flow.

Those skilled in the art will appreciate that elements in the Figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, dimensions may be exaggerated relative to other elements to help improve understanding of the invention and its embodiments. Furthermore, when the terms 'first', 'second', and the like are used herein, their use is intended for distinguishing between similar elements and not necessarily for describing a sequential or chronological order. Moreover, relative terms like 'front', 'back', 'top' and 'bottom', and the like in the Description and/or in the claims are not necessarily used for describing exclusive relative position. Those skilled in the art will therefore understand that such terms may be interchangeable with other terms, and that the embodiments described herein are capable of operating in other orientations than those explicitly illustrated or otherwise described.

Detailed Description of the Preferred Embodiment

Referring to FIGS. 1A- 1C , the fluid restrictors 10, combined with coating (surface treatment on the ID 11 of a capillary tube 12 which is too thin to be illustrated in the drawings) of the capillary tube 12 provide significant advantages when used in a watch such as that described in WO 2011/021097 A4 . The restrictors 10 prevent excessively rapid movement of the meniscus 14 between the two fluids 12 and 20 within the tube, especially when setting the time, or during the return cycle at 6 in the morning or evening (i.e., a retrograde system). Indeed, without them, one of the two liquids 16 and 20, respectively, can disrupt the other, depending on the temperature, by creating a channel 22 in the other.
Note that in some embodiments, the capillary tube 12 is a capillary channel (102) (rectangular, triangular or irregular in cross section), formed in a plate (100), against which the dial (86) is sealingly affixed, such as shown in Figure 7 of WO 2011/021097 A4 . Consequently, the term "tube" and "channel" are intended to mean one and the same thing when recited herein.
The coating improves the behavior of the meniscus 14 against the walls 11 of the capillary and together with an appropriate ratio of the apertures 26 and 34, helps prevent the disruption of the meniscus 14.
The fluid restrictor 10 is preferably a ceramic or stone but may also be a metal. The fluid restrictor 10 is formed as a cap-shaped element having a flange 24 formed thereon which prevents the fluid restrictor from entering the capillary tube 12 more than a prescribed amount. A tiny hole 26 (a few microns in diameter) in the fluid restrictor 10, glued on at least one end 30 of the capillary tube 12, is preferably located along the axis 32 of the fluid restrictor 10. The function of the fluid restrictor 10 is the stability of the meniscus 14, and the protection of the system.
The hole or aperture 26 in the fluid restrictor 10 has a width of between 0.03and 0.1 mm in diameter. The aperture 34 of the capillary tube 12 has a width of between 0.6 and 1 mm, preferably 1 mm in diameter. Preferably, the ratio between the widths of the hole 26 of the fluid restrictor 10 and that of the capillary tube 12 is 5:1 to 15:1, for fluids having viscosities between 0.3 et 80 cP at room temperature, sea level, and preferably 0.3 à 5 cP.
Referring now to FIGs. 2A to 4B , the capillary tube 12 and the fluid restrictor 10 need not have circular inner apertures. In fact, such may be square, triangular, or irregular apertures 26', 26", and 26"', respectively. These may also be adapted to such a non-circular channel (102) formed in the plate (100) shown in Figure 7 of the PCT application.
Referring now to FIG. 5, the hole or aperture 26 of the fluid restrictor 10 is formed such that the exit port of the aperture which exits into the capillary tube 12 enters the capillary tube at an angle to the central axis of the fluid restrictor 10. This reduces the chances that the incoming stream of fluid will disrupt the meniscus 14, particularly when the meniscus 14 is near the fluid restrictor 10, by diverting the flow away from the center of the meniscus 14 to the sides. Still further, several such holes connecting to a single central hole of the fluid restrictor 10 may further help diver the incoming fluid flow away from a center of the meniscus 14.
Referring now to FIG. 6 and 7 , fluid restrictors 10 of the invention, are shown installed in the ends 30 of a single capillary tube 12 (the tube is curved back on itself) with functionality as described in WO 2011/021097 A4 mentioned above. Referring in particular to FIG. 7, ends 30 of the fluid restrictors 10 and capillary tube 12 are shown in cross section, for clarity.
Referring now to FIG. 8 , a fluid restrictor 10 is installed half way into an end 30 of a capillary tube 12, ready to receive a dose of a suitable epoxy.

Gluing tests - Fluid restrictor to capillary

Any number of glues may be used to affix the fluid restrictor 10 to the capillary tube 12. Two have proven to be particularly effective. "VITRALIT"® 1605 from Panacol AG of Steinbach, Germany, diluted with a thinner, is one and has the following characteristics: "VITRALIT"® is thermally cured (30 min @ 105°C) and/or UV cured (60 s @ UV-A 60mW/cm2, thickness step: 0.5 mm). Further, it is a one component epoxy and has a viscosity in the range of 300 - 500 cPs (@25°C).
As for "EPO-TEK"® 301, available from Epoxy Technology, Inc of Billerica, MA is thermally cured (1 hr @ 65°C), is two component (20:5), and has a viscosity in the range of 100 - 200 cPs (@23°C), which is significantly lower than "VITRALIT"®.
Referring now to FIG. 9 , the gluing procedure involves the following steps: In a first step 40, plasma cleaning of both capillary and fluid restrictor is performed. In a second step 42, the fluid restrictor is placed half-way into the capillary tube 12. In a third step 44, a drop of glue is placed on the end 30 of the capillary tube 12 with a standard disposable needle. In a fourth step 46, observing to ensure that the epoxy is properly distributed around fluid restrictor 10. In a fifth step 48, the epoxy is allowed to penetrate around the fluid restrictor and into the capillary via capillary action. In a fifth step 50, the epoxy is allowed to dry or set.
Note that it has been found that "VITRALIT"® 1605 alone is too viscous to promote capillary action between capillary tube 12 and the fluid restrictor 10. To be suitable, it should be thinned with an appropriate thinner, whereas "EPO-TEK"® 301 is suitable without thinning.
Referring now to FIG. 10 , it has been observed that when the glue does not completely surround the fluid restrictor, unacceptable leakage may result.
Again, Vitralit® 1605 is too viscous for capillary action between the capillary tube 12 and the fluid restrictor 10. "EPO-TEK"® 301 is suitable as is. Deposition is critical. If the glue does not surround the fluid restrictor 10, it is not possible to add glue later, or to add glue via the capillary tube 12. Note that these tests were performed with capillary tube 12 having an OD of 02 mm and an ID of Ø1 mm.
As for alternative gluing procedures, inserting a small O-ring 52 around the fluid restrictor 10 helps ensure that the aperture 26 in the fluid restrictor 10 is not blocked by the glue.
Referring now to FIGs. 11 and 12 , the modified procedure for gluing using the O-Ring 52 includes the following steps. In a first step 60, both capillary and fluid restrictor 10 and the O-ring are plasma cleaned. In a second step 62, the O-ring 52 is placed over an end of the fluid restrictor 10. In a third step 64, the fluid restrictor 10 is placed half-way into the capillary tube 12 until the O-ring 52 is in contact with the end rim of the capillary tube. In a fourth step 66, a drop of glue is placed on the exposed circumference of the fluid restrictor 10 with a standard disposable needle or an oil dispenser. In a fifth step 68, the glue is observed to ensure that it penetrates sufficiently. In a sixth step 70, the fluid restrictor 10 is fully inserted into the capillary tube 12 and the O-ring 52 is removed. In a seventh step 72, the epoxy is allowed to dry or cure. O-ring 52 prevents the hole 26 of the fluid restrictor 10 from being clogged by the glue.
Note as well, that in addition to the fluid restrictor 10, a coating of the inside surface 11 of the capillary tube 12 is important to reliable and repeatable control of the meniscus 14 between the fluids in the capillary tube. The fluid restrictors 10 prevent a too rapid movement of the meniscus 14, especially, when the system is used in a watch such as that described in the above identified PCT application, in setting the time, or return at 6 in the morning or evening (retrograde system). Indeed, without these features, the risk is that one of the fluids can create, depending on the temperature, a channel in the other (see FIG. 13 below).
The coating allows it to improve the behavior of the meniscus 14 against the walls 11 of the capillary tube 12.

Claims

A capillary system for a fluid indicator including:
a. at least one fluid restrictor (10) having a small aperture (26, 26', 26") having a characteristic internal aperture width formed therethrough; and

b. a capillary tube (12) having a characteristic internal aperture width much larger to a certain ratio than the characteristic width of the small aperture (26, 26', 26") of the fluid restrictor (10), the capillary tube (12) being adapted to receive at least two immiscible fluids (16, 20), the fluid restrictor (10) being sealingly affixed into at least one end of said tube so that the small aperture (26, 26', 26") communicates between the inside of the capillary tube (12) and the outside of the capillary tube, wherein further, the small aperture (26, 26', 26") of the fluid restrictor (10) has a width of between 0.03 and 0.1 mm.
The capillary system of claim 1, wherein the capillary tube (12) is treated so that an inner surface (11) is oilophobic and hydrophobic.
The capillary system of any one of the above claims, wherein the larger aperture (34) of the capillary tube (12) has a width of between 0.6 and 1 mm.
The capillary system according to claim 1 or claim 2, wherein the certain ratio is in the range of between 5:1 and 15:1.
The capillary system of any one of the above claims, wherein at least one of the apertures (26, 34) is round in cross section.
The capillary system of any one of the above claims, wherein the aperture (26) of the fluid restrictor (10) is formed through a central axis (32) of the fluid restrictor (10).
The capillary system of any one of the above claims, wherein the aperture (26) of the fluid restrictor (10) is formed such that the exit port of the aperture in the fluid restrictor which exits into the capillary tube (12) enters the capillary tube at an angle to the central axis (32) of the fluid restrictor (10).
The capillary system of any one of the above claims, wherein the fluid restrictor (10) is made of ceramic.
The capillary system of any one of the above claims, wherein the fluid restrictor (10) is glued to the capillary tube.
The capillary system of any one of the above claims, wherein the fluid restrictor (10) and the capillary tube (12) are adhered together by an epoxy.
Use of the capillary system of any one of the above claims, in an horological instrument to indicate time.
A method of adhering a fluid restrictor to a capillary tube (12) of the capillary system of claim 1, the method including the steps of:
a. plasma treating the capillary tube (12) and fluid restrictor (10);

b. placing the fluid restrictor (10) approximately half way into the capillary tube (12);

c. placing glue on the capillary tube end preferably with a needle;

d. observing to ensure that glue penetrates sufficiently;

e. inserting the fluid restrictor (10) fully into the capillary tube (12); and

f. allowing the glue to set.
A method of adhering a fluid restrictor (10) to a capillary tube (12) of the capillary system of claim 1, the method including the steps of:
a. plasma treating the capillary tube (12), fluid restrictor (10) and an O-ring (52);

b. placing the O-ring (52) over an end of the fluid restrictor (10);

c. placing the fluid restrictor (10) approximately half way into the capillary tube (12);

d. placing glue on the exposed surface of the fluid restrictor (10), between an end face of the capillary tube (12) and the O-ring (52), preferably with a needle;

e. observing to ensure that glue penetrates sufficiently;

f. inserting the fluid restrictor (10) fully into the capillary tube (12) and removing the O-ring (52); and

g. allowing the glue to set.